'Navy officials said the instability of the ice underscored
growing concern about the changing Arctic environment.

'A breakdown of Camp Nautilus began on Sunday, the Navy said
in the statement. The camp was due to continue supporting
submarine exercises below the surface through March 30.

'Substantial shifts in wind direction created instability in
the Arctic Ocean's wind-driven ice floes, resulting in fractures
in ice near the camp that prevented the use of several
airfields, the Navy said. Small fixed-wing planes or helicopters
are typically used to transport personnel, visitors, and
supplies to the camp.

'This is the first time since 2011 that the U.S. Navy has
built a temporary base camp on the ice far north of Prudhoe Bay
to support submarine exercises. It carried out a similar
exercise in 2012 without a camp.'